Cyclic organopolysiloxane compound

ABSTRACT

The invention provides a novel cyclic organopolysiloxane compound represented by the general formula ##STR1## in which the groups denoted by R, R 1  and R 2  are each typically a monovalent hydrocarbon group having 1 to 8 carbon atoms, m is zero, 1, 2 or 3 and n is 2, 3 or 4 with the proviso that m+n is typically 4. A method for the preparation of the compound is disclosed. The inventive compound is useful as a crosslinking agent of a diorganopolysiloxane terminated at both molecular chain ends each with a silanolic hydroxy group so as to give a room temperature-curable silicone rubber composition free from the problem of emission of toxic or corrosive gases as a byproduct of the crosslinking reaction.

BACKGROUND OF THE INVENTION

The present invention relates to a novel cyclic organopolysiloxanecompound not known in the prior art or not described in any publicationsor, more particularly, the invention relates to a novel cyclicorganopolysiloxane compound useful as a crosslinking agent in a roomtemperature-curable organopolysiloxane composition.

SUMMARY OF THE INVENTION

The novel cyclic organopolysiloxane compound provided by the presentinvention is represented by the general formula ##STR2## in which R is agroup selected from the class consisting of halogenated or unhalogenatedmonovalent hydrocarbon groups having 1 to 8 carbon atoms and atrimethylsiloxy group, R¹ is a hydrogen atom or a substituted orunsubstituted monovalent hydrocarbon group having 1 to 8 carbon atoms,R² is a substituted or unsubstituted monovalent hydrocarbon group having1 to 8 carbon atoms, m is zero, 1, 2 or 3 and n is 2, 3 or 4 with theproviso that m+n is 4 or 5.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 to 8 each show the infrared absorption spectrum of one of theinventive organopolysiloxane compounds prepared in Examples 1 to 8,respectively.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the above description of the inventive organopolysiloxane compound,the symbols R, R¹ and R² each can denote a monovalent hydrocarbon grouphaving 1 to 8 carbon atoms. Such a group is exemplified by alkyl groups,e.g. methyl, ethyl, propyl, butyl and cotyl groups, cycloalkyl groups,e.g. cyclohexyl and cyclopentyl groups, alkenyl groups, e.g. vinyl andallyl groups, aryl groups, e.g. phenyl, tolyl and xylyl groups, andaralkyl groups, e.g. benzyl and 2-phenylethyl groups. The halogenatedmonovalent hydrocarbon group, which may be denoted by R, is exemplifiedby chloromethyl, 3-chloropropyl and 3,3,3-trifuoropropyl groups.

Several of the particular examples of the inventive cyclicorganopolysiloxane compound include those expressed by the followingstructural formulars A to I, in which the symbols of Me, Et, Pr, Bu andOc denote methyl, ethyl, propyl, butyl and octyl groups, respectively,although the present invention is not limited thereto in any way.##STR3##

The most convenient method for the synthetic preparation of theinventive cyclic organopolysiloxane compound of the general formula (I)is as follows. That is, a cyclic organohydrogenpolysiloxane representedby the general formula ##STR4## is subjected to a 1,4-addition reactionwith an α,β-unsaturated ester compound represented by the generalformula

    R'--CH═CR.sup.1 --CO--OR.sup.2,                        (III)

in which R¹ and R² each have the meaning as defined before and R' is anatom or group which makes R'CH₂ -- the same group as R¹, in the presenceof a Wilkinson's catalyst which is a complex compound of rhodium of theformula (Ph₃ P)₃ RhCl, Ph being a phenyl group. The ratio of theunsaturated ester compound of the formula (III) to the cyclicorganohydrogenpolysiloxane of the formula (II) in the reaction mixturein this case should be such that at least 1 mole or, preferably, from1.1 to 1.2 moles of the unsaturated ester compound is provided per moleof the hydrogen atoms directly bonded to the silicon atoms in the cyclicpolysiloxane. The reaction temperature is preferably in the range from60° to 150° C. The reaction mixture may be diluted with an organicsolvent such as benzene, toluene, xylene, hexane and the like.

The cyclic organopolysiloxane compound of the present invention isuseful in various applications, of which the most important applicationis as a crosslinking agent of a diorganopolysilxane terminated at bothmolecular chain ends each with a silanolic hydroxy group as in thediorganopolysiloxane formulated in conventional room temperature-curablesilicone rubber compositions widely used as a sealing and caulkingmaterial, coating material, electric insulating material and the like.The room temperature-curable silicone rubber composition formulated withthe inventive cyclic organopolysiloxane compound as the crosslinkingagent is free from the problem of emission of any toxic or corrosivegases formed as a byproduct of the crosslinking reaction.

In the following, preparation and characterization of several of thecylic organopolysiloxane compounds according to the invention aredescribed in more detail by way of examples which should not beconstrued as limiting in any way.

EXAMPLE 1

Into a three-necked flask of 50 ml capacity equipped with a refluxcondenser, thermometer and dropping funnel were introduced 9.8 g of1,3,5,7-tetramethyl-1,5-bis(trimethylsiloxy)cyclotetrasiloxane, 9.4 g ofmethyl crotonate and 0.01 g of chloro tris(triphenylphosphine)rhodiumand the reaction mixture was agitated for 4 hours at 90° C. by use of anelectromagnetic stirrer. After completion of the reaction, low volatilematters were removed from the reaction mixture by distillation to give14.2 g of a reaction product having a refractive index of 1.421 at 25°C., which was identified to be the cyclic organopolysiloxane of theformula A given before from the results of the infrared absorptionspectroscopy (see the spectrum shown in FIG. 1), NMR analysis andelementary analysis given below. The above mentioned yield of theproduct was 97.7% of the theoretical value.

NMR data: 0.31 (s, Si--CH₃, 3OH), 1.06 (t, C--CH₃, 6H), 2.00 (q, C--CH₂,4H), 3.60 (s, O--CH₃, 6H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.20 H.sub.48 O.sub.10 Si.sub.6                                               38.9     7.8     27.3                                       Found             39.1     7.6     27.0                                       ______________________________________                                    

EXAMPLE 2

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 19.6 g of 1,3,5,7-tetramethyl-1,5-dipropylcyclotetrasiloxane, 12.6 g of methyl crotonate and 0.01 g of the samerhodium complex as used in Example 1 to give 30.6 g of a reactionproduct having a refractive index of 1.433 at 25° C., which could beidentified to be the cyclic organopolysiloxane of the formula B givenbefore from the results of the infrared absorption spectroscopy (see thespectrum shown in FIG. 2), NMR analysis and elementary analysis givenbelow. The above mentioned yield of the product was 97.6% of thetheoretical value.

NMR data: 0.29 (s, Si--CH₃, 12H), 1.10 (t, C--CH₃, 6H), 1.98 (q, C--CH₂,4H), 3.59 (s, O--CH₃, 6H)

    ______________________________________                                        Elementary analysis:                                                                           C, %      H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.20 H.sub.44 O.sub.8 Si.sub.4                                               45.8      8.4     21.4                                       Found            45.7      8.5     21.1                                       ______________________________________                                    

EXAMPLE 3

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 9.7 g of1,3,5,7-tetramethyl-1,5-bis(trimethylsiloxy)cyclotetrasiloxane, 9.6 g ofethyl crotonate and 0.01 g of the same rhodium complex as in Example 1to give 15.0 g of a reaction product having a refractive index of 1.420at 25° C., which could be identified to be the cyclic organopolysiloxaneof the formula C given before from the results of the infratedabsorption spectroscopy (see the spectrum shown in FIG. 3), NMR analysisand elementary analysis given below. The above mentioned yield of theproduct was 99.7% of the theoretical value.

NMR data: 0.31 (s, Si--CH₃, 3OH), 1.08 (t, C--CH₃, 6H), 2.03 (q, C--CH₂,4H), 3.91 (q, O--CH₂, 4H),

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.22 H.sub.52 O.sub.10 Si.sub.6                                               41.0     8.1     26.1                                       Found             41.3     7.9     25.9                                       ______________________________________                                    

EXAMPLE 4

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 10.4 g of1,3,5,7-tetramethyl-1,5-bis(trimethylsiloxy)cyclotetrasiloxane, 7.2 g ofbutyl crotonate and 0.01 g of the same rhodium complex as in Example 1to give 16.2 g of a reaction product having a refractive index of 1.424at 25° C., which could be identified to be the cyclic organopolysiloxaneof the formula D given before from the results of the infraredabsorption spectroscopy (see the spectrum shown in FIG. 4), NMR analysisand elementary analysis given below. The above mentioned yield of theproduct was 92.6% of the theoretical value.

NMR data: 0.30 (s, Si--CH₃, 3OH), 1.06 (t, C--CH₃, 6H), 2.02 (t, C--CH₂,4H), 3.86 (t, C--CH₂, $H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.26 H.sub.60 O.sub.10 Si.sub.6                                               44.5     8.6     24.0                                       Found             44.4     8.5     24.3                                       ______________________________________                                    

EXAMPLE 5

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 10.4 g of1,3,5,7-tetramethyl-1,5-bis(trimethylsiloxy)cyclotetrasiloxane, 15.3 gof 2-ethylhexyl crotonate and 0.01 g of the same rhodium complex as inExample 1 to give 17.5 g of a reaction product having a refractive indexof 1.432 at 25° C., which could be identified to be the cyclicorganopolysiloxane of the formula E given before from the results of theinfrared absorption spectroscopy (see the spectrum shown in FIG. 5), NMRanalysis and elementary analysis given below. The above mentioned yieldof the product was 86% of the theoretical value.

NMR data: 0.25 (s, Si--CH₃, 3OH), 0.8 to 1.7 (m, Oct, 3OH), 2.00 (q,═C--CH₂, 4H), 3.75 (t, O--CH₂, 4H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.34 H.sub.76 O.sub.10 Si.sub.6                                               50.2     9.4     20.7                                       Found             50.0     9.3     20.8                                       ______________________________________                                    

EXAMPLE 6

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 10.4 g of1,3,5,7-tetramethyl-1,5-bis(trimethylsiloxy)cyclotetrasiloxane, 7.3 g ofn-butyl methacrylate and 0.01 g of the same rhodium complex as inExample 1 to give 17.0 g of a reaction product having a refractive indexof 1.426 at 25° C., which could be identified to be a cyclicorganopolysiloxane of the formula F given before from the results of theinfrared absorption spectroscopy (see the spectrum shown in FIG. 6), NMRanalysis and elementary analysis given below. The above mentioned yieldof the product was 97.0% of the theoretical value.

NMR data: 0.28 (s, Si--CH₃, 3OH), 0.9 to 1.5 (m, Bu, 14H), 1.66 (s,═C--C--CH₃, 12H), 3.78 (t, O--CH₂, 4H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.26 H.sub.60 O.sub.10 Si.sub.6                                               44.5     8.6     24.0                                       Found             44.6     8.3     23.8                                       ______________________________________                                    

EXAMPLE 7

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 8.7 g of 1,3,5,7-tetramethyltrimethylsiloxy cyclotetrasiloxane, 10.3 g of methyl crotonate and 0.01g of the same rhodium complex as in Example 1 to give 15.6 g of areaction product having a refractive index of 1.431 at 25° C., whichcould be identified to be the cyclic organopolysiloxane of the formula Ggiven before from the results of the infrared absorption spectroscopy(see the spectrum shown in FIG. 7), NMR analysis and elementary analysisgiven below. The above mentioned yield of the product was 97.9% of thetheoretical value.

NMR data: 0.28 (s, Si--CH₃, 21H), 1.05 (t, C--CH₃, 9H), 1.99 (q, C--CH₂,6H), 3.60 (s, O--CH₃, 9H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.22 H.sub.48 O.sub.11 Si.sub.5                                               42.0     7.7     22.3                                       Found             41.7     7.8     22.4                                       ______________________________________                                    

EXAMPLE 8

The reaction was performed in a similar manner to Example 1 with areaction mixture composed of 4.8 g of 1,3,5,7-tetramethylcyclotetrasiloxane, 11.8 g of butyl crotonate and 0.01 g of the samerhodium complex as in Example 1 to give 15.8 g of a reaction producthaving a refractive index of 1.442 at 25° C., which could be identifiedto be the cyclic organopolysiloxane of the formula H given before fromthe results of the infrared absorption spectroscopy (see the spectrumshown in FIG. 8), NMR analysis and elementary analysis given below. Theabove mentioned yield of the product was 97.6% of the theortical value.

NMR data: 0.40 (s, Si--CH₃, 12H), 0.8 to 1.9 (m, Bu, 28H), 1.98 (q,C--CH₂, 8H), 3.79 (s, O--CH₂, 8H)

    ______________________________________                                        Elementary analysis:                                                                            C, %     H, %    Si, %                                      ______________________________________                                        Calculated as C.sub.36 H.sub.72 O.sub.12 Si.sub.4                                               53.4     9.0     13.9                                       Found             53.2     8.8     14.1                                       ______________________________________                                    

What is claimed is:
 1. A cyclic organopolysiloxane compound representedby the general formula ##STR5## in which R is a group selected from theclass consisting of halogenated or unhalogenated monovalent hydrocarbongroups having 1 to 8 carbon atoms and a trimethylsiloxy group, R¹ is ahydrogen atom or a substituted or unsubstituted monovalent hydrocarbongroup having 1 to 8 carbon atoms, R² is a substituted or unsubstitutedmonovalent hydrocarbon group having 1 to 8 carbon atoms, m is zero, 1, 2or 3 and n is 2, 3 or 4 with the proviso that m+n is 4 or 5.